Bellingham has made his transition to Spanish soccer look ridiculously easy with 11 goals and threes assists in 12 games in all competitions since joining from Borussia Dortmund.
He scored the winner in Real's 2-1 victory at Braga and became only the second Real Madrid player to net in each of his first three Champions League games after Christian Karembeu in 1998.
"(Bellingham) will play because he is felling well, totally recovered. They have removed the overload (in his muscle)," Ancelotti told a press conference on Friday.
"I don't have to explain to him what a Clasico is, everyone knows what it means. It's a worldwide match."
Although acknowledging the massive anticipation surrounding the game, Ancelotti insisted it should not be seen as a final.
"We are motivated, it's an important, special game... But it's only the first Clasico of this season, there will be more... Super Cup, the LaLiga game at our home, Copa del Rey, Champions League.
"There are so many opportunities for us to meet again that makes me have the feeling that tomorrow's game will only be the first of many. And we're in good shape."
Ancelotti said he never had to give explanations to players about his selection decisions, amid concerns about veteran midfielder Luka Modric's role with youngsters like Bellingham, Eduardo Camavinga and Aurelien Tchouameni developing fast.
"Players are all professionals and don't ask for explanations. In the same way, I don't usually give explanations to those who don't play. There is nothing to worry about," Ancelotti said about Modric's role.
"We are working with a new system and things are changing, sometimes we rotate to keep the squad fresh and motivated. That's all."
Real lead the LaLiga standings, level with Girona, the surprise packages of the season, on 25 points from 10 games. Barcelona are third on 24 points, two ahead of Atletico Madrid who have a game in hand.
